The goal of the proposed research is to develop methods for efficient gene transfer and expression in somatic dells as a means for treatment of human disease. The focus of the project will be gene transfer into pluripotent hematopoietic stem cells capable of long-term persistence in animals. While long-term gene expression following hematopoietic stem cell infection has ben documented in the mouse, the same is not true of larger animals. We propose to use dogs as a large animal model to test various strategies for improved stem cell infection, including the use of new hematopoietic growth factors, purified stem cells, gene transfer during long term marrow cultivation, and pretreatment of dogs prior to marrow harvest to increase the susceptibility of stem cells to gene transfer. Skin keratinocytes and bone marrow stromal fibroblasts will also be evaluated as targets for gene therapy.